1. Field of the Invention
The present invention relates to an information processing apparatus which detects the gaze direction of an object, an information processing method for use therewith, and a storage medium for storing a computer program for causing a computer to perform the method.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2003-256852 discloses a technique of detecting the direction of an eye by using a face image including the black parts of the left and right eyes and external canthi. This technique is however designed to estimate only a direction α1 of an eye as shown in FIG. 1 without any consideration to a direction β1 of the face.
Japanese Patent Laid-Open No. 2007-265367 discloses a technique of estimating the gaze direction of an eye (i.e. the direction in which the eye is pointing) from both the direction α1 of the eye and the direction β1 of the face shown in FIG. 1 by detecting feature points such as the eyes from a face in an image and using the distance between the detected feature points (i.e. the distance between the two eyes). Many of the techniques of the background art are designed to calculate the direction α1 of the eye and the direction β1 of the face based on the location relationship between organs (such as nose, eyes, mouth, and their feature points) of the face, as disclosed in Japanese Patent Laid-Open No. 2007-265367. In addition, many techniques estimate a gaze direction from both the direction α1 of the eye and the direction β1 of the face upon separately calculating them.
The first problem is that if the coordinate information of feature points is directly used for gaze detection as in Japanese Patent Laid-Open No. 2007-265367, the feature point detection accuracy itself becomes the estimation accuracy of a gaze direction. That is, the deviation of at least one of detected feature points from a desired position may greatly degrade the gaze detection accuracy.
The second problem is that the technique which separately calculates the direction α1 of the eye and the direction β1 of the face may lead to the accumulation of errors originating from the respective calculations, and hence cannot estimate a gaze direction with high accuracy.
The third problem is that in order to estimate a gaze direction with high accuracy, it is also necessary to consider individual differences such as the sizes of the eyes.
In consideration of the above problems, the present invention provides a technique of estimating a gaze direction with high accuracy independently of individual differences among objects.